Field of the Invention
This invention relates generally to treated carbon fiber tensile cord for reinforced elastomeric composite products such as power transmission belts, more particularly to atmospheric plasma polymerization treatment for carbon cord.
Description of the Prior Art
Carbon fiber tensile cords show potential for reinforcing flexible rubber products subject to dynamic stresses, such as power transmission belts, hose, and tires. Resorcinol-formaldehyde-latex (“RFL”) adhesive treatments are currently in use to facilitate bonding of rubber to carbon fiber. Mechanical interlocking is known to be the main interaction between the fibers and the RFL as compared to chemical bonding. T-block adhesion testing of so treated carbon cords shows separation between the fiber and the RFL. Adhesion between carbon fibers and RFL needs improvement to eliminate the failure mode of delamination of the belt teeth from the cord in current carbon belt systems.
Epoxy primers and/or sizes have been investigated to improve the adhesion of the RFL to carbon fiber surface. However, epoxy primers have not eliminated delamination at the fiber surface layer due to lack of chemical bonding between the epoxy and the fiber surface. Currently, mechanical interlocking of RFL into the carbon fiber tow remains as the primary technique to allow carbon fiber cords to be used in rubber belting.
Previous attempts to use plasma for surface cleaning and for coating or activating cord are known, but have not been found to be satisfactory for the dynamic rubber applications described herein.